Device for emergency shutoff of the pipeline

 

(57) Abstract:

The invention relates to safety appliances for pipes and can be used mainly in gas pipelines under pressure (in some cases in the pipeline with liquefied gas or even liquid) for reliable shutoff in case of their accidental depressurization or in ventilation systems of explosive products for containment of the spill explosive type. Device for emergency shutoff of the pipeline to transport mainly gas under pressure includes a housing with an inlet and outlet, placed in it and shut the sensing elements are made as one whole in the form of a pipe, console and sealed in the output housing bore with the possibility of collapse and locking the pipe in emergency mode currents. The technical result is the comparative simplicity of the design and, consequently, low intensity and cost, greater reliability of operation. 1 C.p. f-crystals, 3 ill.

The invention relates to safety appliances for pipes mainly with gas under pressure and is designed for reliable shutoff in the.with. 1488651 F 16 K 17/22, publ. BI N 23, 23.06.89), providing increased reliability due to reductions in leakage of the working environment.

It when broken pipe under the action of the resulting differential pressure moves the sensing element. At the same time is raspikirovki spring, whose force accelerates the movement of the sensing element. Moving the sensing element is accompanied by release of the locking element in contact with the plunger. Closing element closes the pipeline, excluding the flow medium from the input pipe to the emergency pipeline.

However, when a sufficiently high degree of reliability of this structurally complex system does not provide ravnopravnosti pipeline, making it difficult (or even eliminates) the cleaning.

It is known device is a relief valve.with. 1451398 F 16 K 17/22, publ. BI N 2, 15.01.89), providing for the termination of the emergency gas flow from the damaged pipeline. It contains a stop valve associated kinematic connection with the sensing element of the control mechanism, the working cavity which communicates with the cavity of the outlet pipe, and a stop valve by vypolnyavshemu valve, performed at the outlet port and located at an angle to its axis. The peculiarity of the safety valve is that the fastening of the valve is located under the outlet pipe, the surface of the input end of the tube is located on the path toward her side of the valve, the axis of the input pipe is shifted upward relative to the axis of the output, the diameter of the entrance tube is less than the diameter of the outlet pipe, and in the open position of the valve below the edges of the ends of the pipes are located in the plane of the working surface of the valve, and the surface opposite the working surface of the valve, associated with the surface of the body.

In the event of an accident under the action arose pressure difference between newportnews cavity of the sensing element and the working cavity of the piston sensing element is lowered and causes the movement of the valve. The flap is pressed against the valve seat, blocking the outlet and emergency stopping the outflow of gas.

Providing a high degree of reliability of the valve has the following disadvantages: this structurally complex system does not provide ravnopravnosti pipeline, making it difficult (or even eliminates) h is - recognitory valve.with. 1603122 F 16 K 17/24, publ. BI N 40, 30.10.90), providing for the termination of the emergency gas flow from the damaged pipeline. It includes a housing with inlet and outlet nozzles; the working cavity (chamber) connected through the valve to the pipeline; placed in the enclosure outside the section of the pipe shut-sensitive elements made in one piece in the form of a rotary valve, the surface of which is combined with the input surface of the socket, the hinge connected to the body. In the event of a pipeline rupture pressure in it drops sharply and the working environment comes in the form of jets from the working cavity through the open hole located under the flap; the resulting jet strikes the flap and pulls her; then the flap is caught by the flow of the working medium and locks the pipeline.

The disadvantage of the valve is its relative structural complexity and lack of reliability: the force acting on the valve is determined by the pressure on a limited area (with a characteristic scale of the order of the diameter of the hole), and in some emergency situations (for example, when the rupture of the pipeline is at a relatively great distance from the valve) this forces).

Pipelines are widely used for transporting gases (including liquefied under pressure in many types of industries: chemical, petrochemical and other Natural gas extracted from the fields is transported in transmission pipelines with a diameter up to 1420 mm at a pressure of 75 ATM speeds up to 15 m/s Pipelines are also used in the circuits of nuclear reactors, which pumped as a liquid (in particular, overheated) and gases.

The number of major accidents on pipelines in our country caused great material damage and were the cause of many human victims. In many cases, the depressurization gas pipelines in case of accidents is due to the explosive nature of the propagation of fatigue cracks, or due to the destruction of the pipeline explosion leaked to the atmosphere through a "fistula" combustible gas. The explosive nature can wear depressurization during earthquakes and deliberate bombings of pipelines when sabotage or terrorist acts.

Combustible gases mixed with air to form an explosive mixture. Accidental leakage into the atmosphere of a large volume of gas may be a danger of a large-scale disaster, the explosion of etousa territory.

Rupture of pipelines in the contours of the nuclear reactor can also have severe consequences.

For these reasons, it is important to develop reliable high-speed devices, the locking pipeline accidental rupture of the pipeline.

The proposed device for emergency shutoff of the pipeline (autotutor) has the following advantages:

- comparative simplicity of the design and, consequently, low metal content and value;

- high reliability of operation.

This technical result is achieved due to the fact that in the known device, comprising a housing with inlet and outlet holes placed in it and shut the sensing elements are made as one unit, and the working cavity of the locking element is in communication with the cavity of the pipe, the locking element is designed as pipe, console and sealed in the output housing bore: size, shape, wall thickness and pipe material selected from the condition allow it to collapse and locking the pipe in emergency mode currents.

These conditions are realized in the following design. The connection can be made in the form of a hollow body rotations the ratios

< / BR>
where ; R is the internal radius of the pipe; E, andsthe young's modulus of the material of the pipe and its yield stress in uniaxial tension, respectively; h1the wall thickness of the free end of the pipe, P is the pressure force, shapeways nozzle;

< / BR>
whereinthe tensile strength of the pipe material under uniaxial tension; h2the wall thickness of the pipe in place on the dock; Ps- maximum pressure on the locking element when the emergency pipeline overlap;

L R/arcsinin, (3)

where L is the length of the nozzle;in- deformation shear.

The nozzle may have other forms: it may be a hollow body of rotation, which is cylindrical outer surface and an inner conical; or both surfaces are either cylindrical or conical. The nozzle may have the shape of a regular (or even irregular) hollow prisms, i.e., in cross section it may be correct or incorrect polygon (square, hexagon, rectangle etc). The wall thickness of the faces of these prisms may differ from the adjacent faces within a single pipe.

The shape of the generatrix of the side surfaces of the socket is not necessarily Ave is CLASS="ptx2">

In the General case of complex shape of the nozzle selecting its size can be made by means of numerical calculations for three-dimensional programs with regard to strength (see, for example: A. I. Abakumov, V. Yu.MeItsas, V. P. Soloyjov et al. Dynamic Behaviour Of Composite Shells Under Explosion Load. Computational and Experimental study // Int. Workshop on New Models and Numerical Codes for Shock Wave Processes in Condensed Media, Oxford, Sept. 15-19, 1997].

The pipe Autostore simple to manufacture; due to the small number of parts (pipe and casing) it has a relatively small intensity and cost.

Since the outlet is sealed and a cantilever in the output housing bore when the flow of gas through the pipeline both in the desktop and in the emergency mode, there is a pressure difference between the outer and inner surface of the pipe, since the inside of the nozzle the gas is flowing, and in the working cavity which communicates with the pipe through the gap between the free end of the nozzle and the inlet of the housing) it is almost at rest and pressure are higher than the inside of the pipe, i.e. there is a constant force tending to flatten the pipe, but this was prevented by the strength of the pipe. In the operating mode of the flow in the pipeline power collapse is balanced by the strength Patti pipe; it loses stability and collapses at the free end. The thickness of the wall of the socket in the root (where you attach the pipe to the pipeline) and its length are selected such that after the collapse, he takes the shape of an irregular cone, which locks the pipe and holds the gas.

The working cavity communicates with the pipe through the gap between the free end of the nozzle and the inlet of the housing, which is selected so that the pressure in it was time to adapt to the flow regime in the pipeline in all variants of the operating mode at startup of the pipeline; when it is stopped; fluctuations in the flow rate.

The pressure drop in the pipeline in the event of an accident is a fast acting non-stationary process. Equalization of pressure above and below the pipe due to leakage of gas from the working cavity through the gap in the pipe does not occur instantaneously, but with some delay, and therefore the pipe is the boundary of areas with different pressure, i.e., there is an additional force directed from the periphery to the center and tending to flatten the pipe. Unlike the prototype, in which the force acting on the closing element (flap), is determined by the pressure of Oia is applied to the entire area of the socket, therefore, acting on the nozzle effort will be significantly higher. After the beginning of the collapse of the socket time gasdynamic shapeways force increases, i.e., implemented positive feedback.

At the same time in the desktop mode of operation of the pipeline, when it starts, stop the oscillations of the pressure and velocity of gas flow changes are relatively slow, quasi-static in nature with characteristic times of at least several times, and usually by several orders of magnitude larger than in case of an accident, and as a result, the pressure in the working cavity has time to adjust to the flow in the pipeline. When the gas flow in the channel of the pipeline occurs shapeways force acting on the nozzle and formed due to the asymmetry of the flow inside the pipe (in the pipeline) and outside of the pipe (working cavity). In any case, the flow velocity inside the pipe is higher than the velocity of flow on the outer surface of the pipe (under the pipe in the working cavity, where the gas is practically rests) and as a result there is a pressure difference at the nozzle. For an incompressible fluid pressure shapeways forces for a perfect gas with the adiabatic exponent Poisson

< / BR>
where v, p and velocity pressure="ptx2">

During various modes of operation of the pipeline (start, stop, variations of the flow parameters in the operating mode changes the speed and density of the gas in the pipeline - changing moment shapeways force tending to flatten the pipe. It is therefore necessary to effect shapeways flow, which can be achieved in the operating mode currents were compensated for by the strength of the pipe.

In case of emergency - break the protected section of the pipeline (below or above described device according to the gas flow in the pipeline occurs stationary flow from the fracture to Autostore moving rarefaction wave, the front of which the pressure and density of gas in the pipeline decreases and the speed increases. However due to the fact that the parameters of the gas in the work space does not have time to adapt to rapidly changing parameters of the gas in the pipeline is growing and shapeways force acting on the pipe.

When shapeways force overcomes the force strength, the free end of the pipe loses its stability and he collapses, the angle of attack of the leading edge of the pipe to the flow increases and, accordingly, increases shlaim buckling of the pipe is formula (I), obtained using approximations [, .Lindbergh Increase stresses in the ring with dynamic buckling // In: "Mechanics. New in foreign science. Vol. 8: non-stationary processes in deformable bodies" M.: Mir, 1976, S. 25-50].

The wall thickness of the pipe at the root (where you attach the pipe to the pipeline) and its length are selected such that after the collapse, he takes the shape of an irregular cone, which locks the pipe and keeps the gas; the ability of the explosion of the pipe to maintain the stability and the integrity of the wall where it attaches to the pipeline is determined by the fulfillment of the condition (2) and (3) [C. L. [. Mechanics of thin-walled structures. M.: Mashinostroenie, 1977; Pertsev, A. K., V. E., Dynamics of shells and plates: non-stationary problem. L., Shipbuilding, 1987].

Thus, a pipe Autostore simple to manufacture; due to the small number of parts (pipe and casing), it has a relatively small intensity and cost. Autogator has improved reliability compared to the prototype, in particular, due to the exclusion of failure due to clogging of the holes.

The pipe can be installed symmetrically and asymmetry the CLASS="ptx2">

The design of Autostore will block the pipeline in case of rupture of the downstream gas (of course, this assumes subsonic operating mode of the gas flow in the pipeline). It is possible to install a number of two of the described devices, one of which overlaps the pipeline when the gap downstream, and the second closes the pipe when the gap upstream of the gas. In this case, the second autogator must be installed mirror-symmetrically relative to the first, i.e., the front edge of the nozzle must be positioned relative to the working gas flow is not with the "windward" and "leeward" side.

You can also use this device to prevent rapid flame propagation in ducts filled with a mixture of combustible gases with air (for example, in the channels of ventilation hazardous production facilities), or in drifts underground workings where possible fires and explosions of gases or air-dust mixtures. In this case ahead of the flame front propagated pressure wave (the jump in speed), which can shut autotutor and thereby allow the localization of flame.

It is also possible ACLs products accident explosive type. In this case, the products of the explosion, scattering, create front air compression wave of the jump in speed, under the action of which autogator snap to exit through the ventilation system to the outside of explosion products.

Thus, the simple structure of Autostore combined with its reliability, and simultaneously achieves easy operation: all elements of autotutor are outside the bore of the pipe and enter into section only in case of emergency, which allows periodic cleaning of the pipeline.

The described device can be used mainly in gas pipelines, but under certain conditions can be used in pipelines with liquefied gas (in the case when the accident liquefied gas in the pipe evaporates) and even in pipelines with liquid when the liquid is being pushed by compressed gas).

List of figures.

Fig. 1. Scheme Autostore for the pipeline. Here: 1 - the pipeline; 2 - housing Autostore; 3, 4 - inlet and outlet of the housing; 5 - tube; 6 - working cavity 7 - the gap between the nozzle and the housing, the arrow indicates the direction of flow in the pipeline.

Fig. 2. P CLASS="ptx2">

Fig. 3. Photography node Autostore: (a) the original shape of the pipe; b) the explosion of the pipe.

Information confirming the possibility of achieving a technical result. Scheme specific performance of the proposed device is shown in Fig.1. Here in the cylindrical pipe 1 is mounted a cylindrical housing 2 with an inlet 3 and outlet 4. At the beginning of the outlet housing 4 is mounted locking element in the form of a pipe 5, a console and sealed in the output housing bore size, shape, wall thickness and pipe material selected from the condition allow it to collapse and locking the pipe in emergency mode currents, defined by the relations (1) - (3). The working cavity 6, located between the nozzle 5 and the housing 2 autogator, is connected with the internal volume of the pipe 1 through the gap 7 between the free end of the socket and the housing Autostore.

In the operating mode of the flow in the pipe (in the direction indicated by the arrow) the working cavity 6 through the gap 7 is filled with compressed gas transported by pipeline. For a perfect gas with the adiabatic exponent of the Poisson - pressure braking (working cavity) is RA (for an incompressible fluid the pressure on the locking element is relatively small shapeways power, which is balanced by the strength of the pipe. At the start of the pipeline, it stopped and a small oscillation operating mode, the gas pressure in the working cavity through the gap 7 adjusts the flow in the pipeline. The strength of the wall of the locking element is selected sufficient to compensate for the effect arising shapeways force.

When a disaster occurs the pressure in the gap quickly drops to atmospheric, Autostore is the rarefaction wave and the flow velocity in the area of Autostore increases significantly and, accordingly, increases shapeways force that overcomes the strength of the pipe and if the condition (1) free (thin) edge of the pipe starts to move to the pipeline axis; increases the angle of attack edges of the pipe to the flow; increases shapeways power; as a result, the pipe loses its stability and collapses in front of, acquiring the shape of an irregular cone, which locks the pipeline. If conditions (2) (a necessary condition for stability of the pipe after the collapse), and (3) (a necessary condition for the absence of a shear cantilever edges of the socket at the collapse) the strength of this cone is the e with a sharp pipeline overlap makes for a perfect gas PsP + p (for liquid Psvc).

The installation, which was carried out health check model describes the AZ (Fig. 2), consists of a supply tank 8 of 10 l and embedded in him pipeline 1 (diameter 20 mm), which established the model of autosaver 5 in the form of collapsing pipe of aluminum alloy with AMC cylindrical form: variable internal and external surfaces. As the working environment in the plant was used and the compressed air (b) water, accelerated by compressed air. Working pressure up to 160 bar.

At the end of the pipeline was installed aperture 9 and rapid depressurization of the pipeline (fracture aperture).

During the experiment the closed volume of the installation is filled with compressed air to a predetermined pressure and then made a breakthrough aperture and starts the outflow of gas from a supply tank through a pipeline (in experiments with compressed air).

Conducted a series of experiments that varied the initial gas pressure. In the varied speed of air flow through the pipeline and, consequently, the value of shapeways forces on the pipe model autosaver. It was the definition of the e Shelbyville. Analysis of experimental results shows that the obtained value is a critical value of pressure is consistent with conditions (1)-(3).

Was also undertaken a series of experiments with water in which the tank was partially filled with water, driven by compressed air. In these experiments, the pipe is not Shelbyville at a pressure less critical and Shelbyville at a pressure exceeding a critical value.

Thus, the experiments confirmed the reliability of operation a simple design of pipe Autostore under critical flow parameters.

1. Device for emergency shutoff of the pipeline to transport mainly gas under pressure, comprising a housing with inlet and outlet holes placed in it and shut the sensing elements are made as one unit, and the working cavity of the locking element is in communication with the cavity of the pipe, characterized in that the locking element is designed as pipe, console and sealed in the output housing bore with the possibility of collapse and locking the pipe in emergency mode currents.

2. The device under item 1, characterized in that the nozzle is ture and materials which are defined by the relations

< / BR>
where

R is the internal radius of the pipe;

Esthe young's modulus of the material of the pipe and its yield stress in uniaxial tension, respectively;

h1the wall thickness of the free end of the nozzle;

P is the pressure force, shapeways pipe in emergency mode;

L R/arcsinin,

where L is the length of the nozzle;

in- deformation shear,

< / BR>
where in- the tensile strength of the pipe material under uniaxial tension;

h2the wall thickness of the pipe at the place of installation;

Rs- maximum pressure on the locking element when the emergency pipeline overlap.

 

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